fpf{-}inv{-}rename($r$;${\it rinv}$;$f$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$\langle$mapfilter($\lambda$$x$.outl(${\it rinv}$($x$));$\lambda$$x$.isl(${\it rinv}$($x$));1of($f$))$,\,$2of($f$)$\,\circ\,$$r$$\rangle$